1. Field of Invention
This invention relates to a method for producing a centralized distribution unit to be used for providing a central distribution to stator windings of a thin brushless motor for a vehicle.
2. Description of Related Art
Recently, automobiles with good fuel economy have been in high demand. As one example of automobile manufacturers' efforts to meet these demands, hybrid cars with super low fuel consumption have been developed. In particular, a hybrid car has been proposed recently which is provided with an auxiliary power mechanism (a motor assist mechanism) in which an engine provides the main power and a DC brushless motor assists the engine upon acceleration or the like.
The motor assist mechanism is subject to much constraint in installation, since a brushless motor constituting the motor assist mechanism is disposed in a limited space, for example, a space between an engine and a transmission in an engine compartment. Thus, such a brushless motor is required to have a thin configuration.
A thin brushless motor to be used in the motor assist mechanism of a vehicle includes a rotor directly connected to a crankshaft of the engine, and a ring-like stator enclosing the rotor. The stator includes many magnetic poles that have windings on cores, a stator holder that contains the magnetic poles, and a centralized distribution unit that concentratedly distributes currents to the windings.
For convenience of explanation, a prior art centralized distribution unit to be used in a three-phase DC brushless motor will be described with reference to FIGS. 33A and 33B. FIG. 33A is perspective view of ring-like bus bars. FIG. 33B is a plan view of a conductive metallic plate from which the ring-like bus bars are to be punched out.
The centralized distribution unit, as shown in FIG. 33A, includes three ring-like bus bars 101, 102, and 103. Each of the ring-like bus bars 101, 102, and 103 includes a ring-like body 104, a terminal portion 105 projecting outwardly in a radial direction on an outer periphery of the ring-like body 104, and a plurality of tabs 106 each projecting inwardly in the radial direction on an inner periphery of the ring-like body 104. Each terminal portion 105 is electrically connected through an electric wire to a battery while each tab 106 is electrically connected through a respective electric wire to an end of a respective winding. When the three ring-like bus bars 101, 102, and 103 are energized, currents are concentratedly distributed to the windings corresponding to a U phase, a V phase, and a W phase. Consequently, the motor is driven.